Dry-break couplers are commonly used to provide for quick coupling and decoupling of fluid conduits. A dry-break coupler generally comprises a pair of disconnectably connectable coupling members, each having a poppet valve by means of which fluid flow may be controlled. When the coupling members are connected together, the poppet valves may be opened, thus forming a flow passage for the transfer of fluids, primarily liquids, through the coupler. One such coupler is described in U.S. Pat. No. 3,473,569.
The operation of a prior art dry-break coupler is illustrated in FIGS. 1a-1c. A coupler valve comprises a first coupling member 10 and a second coupling member 20, each comprising respective housings 19, 29 and having respective poppet valves 14, 24. The first coupling member 10, which may be connected to a ship (not shown), is connectable to the second coupling member 20, which may be connected to a hose (not shown) via a clamp arrangement 12, in a manner which is known in the art.
FIG. 1a shows the two coupling halves in a disconnected and closed state, i.e. where the poppet valves prevent flow through the respective coupling housing. FIG. 1b shows the dry-break coupler in a connected and open state, i.e. where the poppet valves 14, 24 have been activated (in a manner known in the art via i.a. the spring 21), thus allowing a flow F (of e.g. oil or an oil/gas mixture) from the hose, through the coupler and into the ship. FIG. 1c shows the coupler in a connected and closed state, i.e. where the poppet valves have been closed, thus preventing fluid flow through the housings. The state illustrated by FIG. 1c is representative of the state immediately before disconnection of the two couplers.
Present dry-break couplers are constructed in such a manner that spillage of fluids upon coupling and/or decoupling of the coupling members is reduced to a minimum. However, a problem with prior art dry-break couplers is that even such devices have a tendency to lose an, albeit small, quantity of fluid during uncoupling. In particular, large couplers (in the oil and gas industry, commonly 20″ diameter) are designed with a certain tolerance, leaving an effective volume between the mating surfaces in which liquids and/or gases will accumulate when the poppet valves close prior to coupler disconnection. This is illustrated by FIG. 2, identifying the mating region M1 of the two coupling housings 19, 29 and the mating region M2 of the two poppet valves 14, 24, and showing the coupler in a connected and closed configuration (cf. FIG. 1c), and the resulting volume 2 in the mating regions M1, M2 where residual fluids will accumulate when the poppet valves are closed but before the couplers members are disconnected. Reference number 11 denotes a coupler seal. Where such coupling devices are used in fluid systems containing fluids which are of a dangerous nature or in pristine environments, spillage of such residual fluid contained by the volume 2 is particularly undesirable, even though it may be a comparably small volume.
In the hydrocarbon transport industry, dry-break couplers have been used on the ends of loading arms for coupling to loading adapters on transportation vehicles such as tank trucks and ships. For example, large couplers for transferring oil and/or gas between ships and offshore production plants or onshore plants are used extensively world-wide. Dry-break couplers are normally arranged more or less horizontally and above a deck structure or similar, whereby the residual fluids in the volume 2 may be collected by a drip tray, or similar, when the couplers are disconnected.
However, offshore loading and dynamic positioning now require couplers which are movable, suspended from the ship and hanging (e.g. by cardanic suspension) above the water surface (with no intermediate structure onto which a drip tray may be placed). These couplers are connected and disconnected in a vertical—or near vertical—position, above the sea.
It is therefore a need for a device and a method for reducing spillage of residual fluids upon disconnecting a coupler.
The present applicant has devised and embodied this invention to overcome the shortcomings of the prior art, and to obtain further advantages.